A better control over processes responsible for the photocurrent generation in semiconductors and nanocomposites is essential in the fabrication of photovoltaic devices, efficient photocatalysts and optoelectronic elements. Therefore, new approaches towards photochemical properties tuning are intensively searched for. Among numerous parameters, the photocurrent polarity is of great importance to the overall performance of a device. Usually, the polarity is controlled through an alignment of electronic states/bands, tailoring of applied potential or suitable selection of incident light wavelengths. In most scenarios though, the influence of light intensity is somehow neglected and either some arbitrarily chosen, natural conditions are mimicked or this parameter is varied only in a narrow range. Here we present a ternary nanocomposite in which the persistent photocurrent polarity switching is achieved through changes in the light intensity. We also present arguments suggesting this behaviour is of a general character and should be considered also in other photochemical systems.

This review focuses on the synthesis, properties and selected applications of heavy pnictogen chalcohalides, i.e. compounds of the MQX stoichiometry, where M = As, Sb, and Bi; Q = O, S, Se, and Te; and X = F, Cl, Br and I. The first section focuses on their synthesis and crystal structures, and the second section discusses the electronic structure on the basis of quantum chemical modelling and selected experimental data. Finally, the third section discusses their electrical, photoelectrochemical and photocatalytic properties and applications. In contrast to perovskites, chalcopyrites and kesterites, chalcohalides have attracted relatively less attention, but their structure and properties are well suited for numerous applications.

Since the discovery of memristors, their application in computing systems utilizing multivalued logic and a neuromimetic approach is of great interest. A thin film device made of methylammonium bismuth iodide exhibits a wide variety of neuromorphic effects simultaneously, and is thus able to mimic synaptic behaviour and learning phenomena. Standard learning protocols, such as spike-timing dependent plasticity and spike-rate dependent plasticity might be further modulated via metaplasticity in order to amplify or alter changes in the synaptic weight. Moreover, transfer of information from short-term to long-term memory is observed. These effects show that the diversity of functions of memristive devices can be strongly affected by the pre-treatment of the sample. Modulation of the resistive switching amplitude is of great importance for the application of memristive elements in computational applications, as additional sub-states might be utilized in multi-valued logic systems and metaplasticity and memory consolidation will contribute to the development of more efficient bioinspired computational schemes.

Graphene oxide (GO) was modified by two modified porphyrins (THPP and TCPP) to form GO–porphyrin hybrids. Spectroscopic measurements demonstrated the formation of stable supramolecular aggregates when mixing two components in solution. The Fourier transform infrared (FTIR) and Raman scattering measurements confirm π-stacking between hydrophobic regions of GO nanoflakes and porphyrin molecules. On the number and the kind of paramagnetic centers generated in pristine GO samples, which originate from spin anomalies at the edges of aromatic domains within GO nanoflakes. More significant changes in electronic properties have been observed in hybrid materials. This is particularly evident in the drastic increase in the number of unpaired electrons for the THPP-GO sample and the decrease in the number of unpaired electrons for the TCPP-GO. The difference of paramagnetic properties of hybrid materials is a consequence of π-stacking between GO and porphyrin rings. An interesting interplay between modifiers and the surface of GO leads to a significant change in electronic structure and magnetic properties of the designed hybrid materials. Based on the selection of molecular counterpart we can affect the behavior of hybrids upon light irradiation in a different manner, which may be useful for the applications in photovoltaics, optoelectronics, and spintronics.